Section 2.2 measuring Earthquakes

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Vocabulary

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Focus: the point beneath Earth's surface where rock that is under stress breaks

Epicenter: point directly above the focus

Seismic waves: vibrations that travel through Earth's surface carrying the energy created by an earthquake

Primary waves: the earthquake waves that compress and expand the ground like an accordion

Secondary waves: the waves that vibrate from side to side as well as up and down

Surface waves: when Primary waves and Secondary waves reach the surface some of them are transformed into Surface waves

Seismograph: the instrument that geologist use to record and measure the vibration of seismic wave

Magnitude: the measurement of earthquake strength based on seismic waves and movement a long faults

Mercalli Scale: rate earthquakes by their intensity

Richter Scale: rate earthquakes by mechanical seismograph

Moment Magnitude Scale: rates earthquakes by estimating the total energy released

Outline

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Seismic Waves

-P waves
compress and expands the ground
-S waves
vibrates the Earth side to side and up and down
-Surface waves
shake buildings side to side

Detecting Seismic Waves

-seismograph


Measuring Earthquakes

-Mercalli scale
measures by intensity

-The Richter scale
measures by a type of mechanical seismograph

-Moment magnitude scale
estimates the total amount of energy released

Locating the epicenter

-uses seismic waves